Have read much on this forum and elsewhere about the 3000 rpm "miss." We bought our '94 new 9/94 and it has had the miss since about 20K miles (83K on engine today).

Some time ago I had an oil leak and in the process of fixing it, happened to clean up the throttle butterflies and throats. The 3K rpm miss went away for a while, but returned after about 500 more miles.

Today I was into the throttle body again and noticed the Allen screw/locknut combo that sets the double throttle closed position was allowing the butterflies to close completely. Whenever I manually opened them, they were slightly sticky (after cleaning) just at opening. So I adjusted the Allen screw so that the double butterflies are just not quite closed (REALLY close, but just not quite closed). And the 3K rpm miss is gone again.

I had not made this adjustment during the last cleaning; am hoping this cleaning and slight adjustment will clear the miss once and for all.

 

Do everything you can to eliminate the hesitation. Not just one thing at a time. Check all the contact points on the ground wire(s). The main one is right underneath the oil filter and one on the firewall right behind the UIM. Use the process of elimination to get rid of that pesky 3k hesi.

 

DUDE, did you even read what he posted?

He posted a finding to fixing it, and resulted in it NOT hesitating anymore...

 

What are u talkin about when u say butterflies and the throat. You said the butterflies close completely. Are you talkin about the flat piece in there that opens and closes?

 

PhoenixDownVII,

You are correct.

MazdaSpeed93,

"Butterflies" = the flappers in the throttle body, as you wrote.
"Throat" = the throttle body's bore through which air flows.

Primary throttle is at the bottom. The "double throttle" is at the top, which has the adjustment on the left at the top using an Allen screw and locknut. That's the adjustment I mean. If you have the 3K rpm miss, remove your air tube to the throttle body (one big air hose, one small air hose, and 4 nuts). Manually open the upper butterflies, gently, and if they are fully sealed shut, you will feel a slight stickiness just as they open. You can eliminate that stickiness by adjusting that external Allen screw. Just a touch, so that the butterflies no longer stick when opening. You don't want to let any more air than absolutely necessary through that path when they are at closed position. Try it, & post back here if it works (or not).

 

Did you disconect the battery when you were working on the TB? and/or when you fixed the oil leak?

 

Gadd,

No, neither job required disconnecting the battery. The only electrical item was during the first job when I had to remove the oil pressure sensor to get at one of the pedestal nuts, and there is no power to that when ignition is off.

 

Hmm, this sounds interesting, and would coincide with the fact that once the engine is warmed up, the 3K hesitation disappears (at least on my FD). When I install my ASP IC, I'm going to check this out (since I have to use a Greddy elbow, requiring removal of the stock TB elbow). You'd have to be extremely careful not to open the throttle butterfiles too much and affect the idle. You didn't have to do any idle adjustment or notice any differences there, did you?

 

Ya, the flat piece is the butterfly

 

Kento,

Yes, there was a very slight increase in idle rpm. I compensated for it easily by adjusting the the idle speed air bypass screw in the lower right corner of the TB, with the "TEN" terminal of the Diagnostic Connector connected to its "GND" terminal. No sweat. I should have mentioned it, though.

 

Interesting! Made me go out and pull my throttle body...

My TB has the secondary plates just right - they easily pull open, no sticking, and they're fully closed at rest. But, I found my primary throttle plate was adjusted open a bit - closed it, and also readjusted the dashpot.

Drove around the block, and I do still get some hesitation - I'll have to try tomorrow when the car is cold. I get just a light stumble at 3000 RPM - nowhere near the violent jerk I've seen in some FDs.

I do also have ground straps - one going to the frame, and the other going to the ground point on top of the rotor housings for the ECU. Tonight I cleaned the main engine ground and re-toruqued it as well.

We'll see .

I just plan on getting a PowerFC at some point and waving the hesistation bye-bye .

Dale

 

anybody else tried this? is the hesitation gone with this adjustment?

 

I removed my secondaries flappers a while back. I still got it.

 

PFC solved my hesitation/bucking (it was between 1500-2300) or so. I believe it solved other peoples problem as well. I think these issues are ecu related (and maybe TPS as well).

I hope the "butterflies" solve the problem. I'm guessing the problem will come back though. It would go away when I do some maintenance issue, then come back later. Its like a recurring itch that wont go away until you apply some PFC to it

 

POS7 is right, at least as far as my RX-7 is concerned. When I wrote the original post, the 3K rpm hesitation had gone away, but recently it has come back. Replacing all the vacuum hoses didn't fix it either. Bummer.

 

when I moved my ait sensor to the elbow 98% of the stumbles went away. I had both the 2200 and the 3100 stumble......

 

I have read alot on this and come to the conclusion that it is more of an electrical issue than anything, which makes since to me for the way the car acts when it happens, that is why when people get an upgraded electrical system like the hks or jacobs it goes away and even the power fc fixes it too.
Thomas

 

I agree. My double throttle is disabled, and I still get a minor hesitation sometimes. It's never violent.

 

I think he is talking about the butterflies that are controlled by the throtle

 

Yep, when I had a stock ECU without secondary butterflies, i still got it (often violent). But as far as i remember, when I jumpered the fuel pump in the diagnostics box, i NEVER got the hesitation. 0.02

 

If you removed the butterflies he is talking about your car would constantly be at red line.

 

Replacing the IAT sensor ($60) or adjusting the TPS probably won't fix it either.

this may work, never tried it though.



The stock ecu has to deal with all the emmission crap (eliminated with aftermarket ecu) that may affect the way the car delivers fuel/spark

I've heard that the PFC has stumbling issues if the 4 wires dealing with the emmission stuff isn't cut. I'm not sure how similar it is to the hesitation/bucking with the stock ecu.

 

It is completely different - car will not even idle properly if these four wires are not cut.

I installed a PFC a few weeks ago and the hesitation that I had (that was frequently harsh) is completely history - not even a hint of it remains. Car is also a lot smoother.

 

When i swapped out my stock ecu for my m2 stage 3 there was no stumble at all,it was seamless like a single turbo.That lasted about 2 days and the slight stumble came back with the m2.